General Description
The MAX16023/MAX16024 low-power battery-backup cir-cuits with a regulated output are capable of delivering up to 100mA output current. The MAX16023/MAX16024include a low-dropout regulator, a microprocessor (μP)reset circuit, and a battery switchover circuit. Additional available features include a manual reset, a power-fail comparator, and a battery-on indicator. These devices reduce the number of external components to minimize board space and improve reliability.
The MAX16023/MAX16024 are ideally suited for provid-ing power for backing up critical memory such as static random-access memory (SRAM) or real-time clocks (RTCs). The regulated output is powered by V CC when it is present and switches over to the backup power dur-ing brownout. The MAX16023/MAX16024 accept an input voltage from 1.53V to 5.5V and provide fixed stan-dard output voltages of 1.2V, 1.8V, 2.5V, 3.0V, and 3.3V.The MAX16024 offers the ability to externally set the out-put voltage using a resistive divider. All outputs are available with push-pull or open-drain configurations.The MAX16023 offers a power-fail comparator for monitor-ing an additional voltage or for providing an early power-fail warning. Another feature includes a manual-reset input (MAX16023/MAX16024). The MAX16024 also features a battery-on indicator and chip-enable gating function.The MAX16023/MAX16024 are offered in 8- and 10-pin TDF N packages and are fully specified from -40°C to +85°C temperature range.
Applications
Main/Backup Power for RTCs/SRAM Industrial Controls GPS Systems Set-Top Boxes
Point-of-Sale Equipment Portable/Battery Equipment
Features
o System Monitoring for 5V, 3.3V, 3V, 2.5V, or 1.8V Power-Supply Voltages
o 100mA Low-Dropout Regulator
o Factory-Trimmed and Adjustable Output Voltages o 1.53V to 5.5V Operating Voltage Range o Low-Power Consumption: 4μA (typ)
o Power-Fail Comparators for Monitoring Voltages Down to 0.6V o Battery-On Indicator o Battery Freshness Seal
o On-Board Gating of CE Signals, 1.5ns Propagation Delay (MAX16024)o Debounced Manual-Reset Input o 145ms (min) Reset Timeout Period o Tiny 8-Pin and 10-Pin TDFN Packages o UL ?Certified to Conform to IEC60950-1
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
19-4249; Rev 0; 8/08
For pricing, delivery, and ordering information,please contact Maxim Direct at 1-888-629-4642,or visit Maxim’s website at https://www.doczj.com/doc/9814812567.html,.
Ordering Information
The first placeholder “_” designates reset output options. A letter “L” in this placeholder indicates a push-pull output and letter “P”indicates an open-drain output. The next placeholder “_” desig-nates the reset threshold (Table 1). The last two placeholders “_ _” designate output voltage (Table 2). For the MAX16024 with adjustable output voltage version, there are no last two place-holders.
+Denotes a lead-free/RoHS-compliant package.T = Tape and reel.*EP = Exposed pad.
Pin Configurations
UL is a registered trademark of Underwriters Laboratories, Inc.
M A X 16023/M A X 16024
Battery-Backup Circuits with Regulated Output Voltage 2_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V CC = 1.53V to 5.5V, V BATT = 3V, reset not asserted, T A = T J = -40°C to +85°C, C OUT = 10μF, unless otherwise noted. Typical val-ues are at T A = T J = +25°C.) (Note 2)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
V CC , BATT, OUT to GND..........................................-0.3V to +6V RESET , PFO , BATT ON (all open drain)
to GND..................................................................-0.3V to +6V RESET , PFO , BATT ON (all push-pull)
to GND .................................................-0.3V to (V OUT + 0.3V)PFI, CE IN, CE OUT to GND.......................-0.3V to (V OUT + 0.3V)MR to GND.................................................-0.3V to (V CC + 0.3V)Input Current
V CC Peak Current.....................................................................1A V CC Continuous Current...............................................250mA BATT Peak Current.......................................................500mA BATT Continuous Current...............................................70mA
Output Current
OUT Short Circuit to GND Duration....................................10s RESET , BATT ON, CE OUT..............................................20mA Continuous Power Dissipation (T A = +70°C)
8-Pin TDFN (derate 24.4mW/°C above +70°C).........1951mW 10-Pin TDFN (derate 24.4mW/°C above +70°C).......1951mW Thermal Resistance (Note 1)
θJA (8-Pin and 10-Pin TDFN)........................................41°C/W Operating Temperature Range ...........................-40°C to +85°C Junction Temperature......................................................+150°C Storage Temperature Range.............................-65°C to +150°C Lead Temperature (soldering, 10s).................................+300°C
Note 1:Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to https://www.doczj.com/doc/9814812567.html,/thermal-tutorial .
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
ELECTRICAL CHARACTERISTICS (continued)
(V CC = 1.53V to 5.5V, V BATT = 3V, reset not asserted, T A = T J = -40°C to +85°C, C OUT = 10μF, unless otherwise noted. Typical val-ues are at T A = T J = +25°C.) (Note 2)
M A X 16023/M A X 16024
Battery-Backup Circuits with Regulated Output Voltage 4_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
BATT CC BATT Note 4:Dropout voltage is defined as (V IN - V OUT ) when V OUT is 2% below the value of V OUT when V IN = V OUT + 1V.Note 5:CE IN to CE OUT resistance is tested with V CC = 5V and V CE IN = 0 or 5V.Note 6:Use external current-limiting resistor to limit current to 20mA (max).
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
_______________________________________________________________________________________5
V CC SUPPLY CURRENT vs. V CC SUPPLY VOLTAGE
V CC SUPPLY VOLTAGE (V)
V C C S U P P L Y C U R R E N T (μA )
3.0
2.5
4.5
2.0
3.5
5.0
4.0
5
10
15
20
25
01.5
5.5
V CC SUPPLY CURRENT vs. TEMPERATURE
TEMPERATURE (°C)
V C C S U P P L Y C U R R E N T (μA )
60
10
35
-15
2468101
35790-40
85
BATT SUPPLY CURRENT vs. V CC SUPPLY VOLTAGE
V CC SUPPLY VOLTAGE (V)
B A T T S U P P L Y
C U R R E N T (μA )
1.0
3.0
0.5
2.5
2.0
1.5
2
4613
500
3.5
BATTERY SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
B A T T E R Y S U P P L Y
C U R R E N T (μA )
60
10
35
-15
12
34
50-40
85
BATT STANDBY CURRENT vs. TEMPERATURE
TEMPERATURE (°C)
B A T T S T A N D B Y
C U R R E N T (n A )
60
10
35
-15
-6-2
2610-8
-4048-10
-40
85
RESET OUTPUT VOLTAGE LOW
vs. SINK CURRENT
SINK CURRENT (mA)
O U T P U T V O L T A G E L O W (V )
16
8
12
4
0.2
0.4
0.6
0.8
1.0
00
20
146
102
18Typical Operating Characteristics
(V CC = 5V, V BATT = 0, I OUT = 0, T A = +25°C, unless otherwise noted.)
Table 1. Reset Threshold Ranges
M A X 16023/M A X 16024
Battery-Backup Circuits with Regulated Output Voltage 6_______________________________________________________________________________________
Typical Operating Characteristics (continued)
(V CC = 5V, V BATT = 0, I OUT = 0, T A = +25°C, unless otherwise noted.)
V CC FALLING TO RESET DELAY
vs. TEMPERATURE
TEMPERATURE (°C)D E L A Y (μs )
60
10
35
-15
2040608010010305070900-40
85RESET TIMEOUT PERIOD vs. TEMPERATURE
M A X 16023 t o c 08
TEMPERATURE (°C)R E S E T T I M E O U T P E R I O D (m s )
6035-1510185190195200210205215220
180
-4085NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
TEMPERATURE (°C)
N O R M A L I Z E D R E S E T T H R E S H O L D
601035-150.9901.0051.0151.0200.9850.9951.0001.0100.980
-40
85
MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE
RESET THRESHOLD OVERDRIVE (mV)T R A N S I E N T D U R A T I O N (m s )
20040060080010000255075100125
150175200DROPOUT VOLTAGE vs. LOAD CURRENT
LOAD CURRENT (mA)
D R O P O U T V O L T A G
E (m V )
80406020150350450500100300502002504000
0100
7030501090OUTPUT VOLTAGE vs. LOAD CURRENT
LOAD CURRENT (mA)O U T P U T V O L T A G E (V )
804060202.422.582.662.70
2.382.542.342.462.502.622.30
100
7030501090
OUTPUT VOLTAGE vs. V CC VOLTAGE
V CC VOLTAGE (V)
O U T P U T V O L T A G E (V )
1
4
2.12.52.72.82.02.41.91.81.71.62.22.32.61.5
6
2
3
5
LOAD-TRANSIENT RESPONSE
MAX16023 toc14
1ms/div
OUT
AC-COUPLED 100mV/div
50mA I OUT
20mA/div 10mA
MAX16024PTBS25+
C OUT = 10μF
STARTUP RESPONSE
MAX16023 toc15
2ms/div
V CC 2V/div
OUT 1V/div MAX16024PTBS25+I OUT = 0MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
_______________________________________________________________________________________7
MR FALLING TO RESET DELAY
MAX16023 toc16
200ns/div MR 5V/div
RESET 5V/div CHIP-ENABLE LOCKING OUT SIGNAL DURING RESET
MAX16023 toc17
40μs/div
2V/div
2V/div
RESET 5V/div Typical Operating Characteristics (continued)
(V CC = 5V, V BATT = 0, I OUT = 0, T A = +25°C, unless otherwise noted.)
M A X 16023/M A X 16024
Battery-Backup Circuits with Regulated Output Voltage 8_______________________________________________________________________________________
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
_______________________________________________________________________________________9
Functional Diagrams
M A X 16023/M A X 16024
Battery-Backup Circuits with Regulated Output Voltage 10______________________________________________________________________________________
Functional Diagrams (continued)
Detailed Description
The Typical Applications Circuit shows a typical con-nection using the MAX16024. OUT powers the SRAM. If V CC is higher than the reset threshold (V TH ), or if V CC is lower than V TH but higher than V BATT , the regulator is powered from V CC . If V CC < V TH , V CC < V BATT , and the regulator is in dropout, the regulator is powered from BATT (see the Functional Diagrams ). OUT supplies up to 100mA from V CC .
Backup-Battery Switchover
In a brownout or power failure, it may be necessary to preserve the contents of the RAM. With a backup-bat-tery installed at BATT, the MAX16023/MAX16024 auto-matically switch the RAM to backup power when V CC falls. The MAX16024 has a BATT ON output that goes high when in battery-backup mode. Three conditions must be met for these devices to switch to battery backup mode:
1) V CC is lower than the reset threshold.2) V CC is lower than V BATT .
3) The regulator is in dropout (except for the 1.2V out-put version).
Chip-Enable Signal Gating (MAX16024)
The MAX16024 provides internal gating of CE signals to prevent erroneous data from being written to CMOS RAM in the event of a power failure or brownout. During normal operation, the CE gate enables and passes all CE transitions. When the reset output asserts, this path becomes disabled, preventing erroneous data from cor-rupting the CMOS RAM and CE OUT is pulled up to OUT through an internal current source. The 1.5ns propaga-tion delay from CE IN to CE OUT allows the devices to be used with most μPs and high-speed DSPs.
During normal operation (reset not asserted), CE IN is connected to CE OUT through a low on-resistance transmission gate. If CE IN is high when a reset asserts,CE OUT remains high regardless of any subsequent transition on CE IN during the reset event.
If CE IN is low when reset asserts, CE OUT is held low for 12μs to allow completion of the read/write operation.After the 12μs delay expires, CE OUT goes high and stays high regardless of any subsequent transitions on CE IN during the reset event. When CE OUT is discon-nected from CE IN, CE OUT is actively pulled up to OUT.The propagation delay through the chip-enable circuitry depends on both the source impedance of the drive to CE IN and the capacitive loading at CE OUT. Minimize the capacitive load at CE OUT to minimize propagation delay, and use a low-output-impedance driver.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
______________________________________________________________________________________11
Figure 1. Reset and Chip-Enable Timing
M A X 16023/M A X 16024
Manual-Reset Input (MAX16023/MAX16024)
Many μP-based products require manual-reset capabili-ty, allowing the operator, a test technician, or external logic circuitry to initiate a reset. F or the MAX16023/MAX16024, a logic-low on MR asserts RESET . RESET remains asserted while MR is low. When MR goes high,RESET deasserts after a minimum of 145ms (t RP ). MR has an internal 30k Ωpullup resistor to V CC . MR can be driven with TTL/CMOS logic levels or with open-drain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manual-reset function; external debounce circuitry is not required. If MR is driven from a long cable or the device is used in a noisy environment, connect a 0.1μF capaci-tor from MR to GND to provide additional noise immunity.
Battery-On Indicator (MAX16024)
The MAX16024’s BATT ON output goes high when in battery-backup mode. Use BATT ON to indicate bat-tery-switchover status.
Battery Freshness Seal
The MAX16023/MAX16024 battery freshness seal dis-connects the backup battery from internal circuitry and OUT until V CC is applied. This ensures the backup bat-tery connected to BATT is fresh when the final product is used for the first time.
The internal freshness seal latch prevents BATT from powering OUT until V CC has come up for the first time,setting the latch. When V CC subsequently turns off,BATT begins to power OUT.
To reenable the freshness seal (MAX16023/MAX16024):
1) Connect a battery to BATT.2) Bring V CC to 0.
3) Drive MR higher than V BATT + 1.2V for at least 3μs.4) Pull OUT to 0.
Reset Output (MAX16023/MAX16024)
A μP’s reset input starts the μP in a known state. The MAX16023/MAX16024 μP supervisory circuits assert a reset to prevent code-execution errors during power-up, power-down, and brownout conditions. RESET asserts when V CC is below the reset threshold and remains low for at least 145ms (t RP ) after V CC rises
above the reset threshold. RESET also asserts when MR is low. RESET is available in both push-pull and open-drain configurations.
Power-Fail Comparator (MAX16023)
The MAX16023 offers an additional undervoltage com-parator. The output PFO goes low when the voltage at PFI falls below its V PFT threshold. Common uses for the power-fail comparator include monitoring the input of the power supply (such as a battery) before any voltage reg-ulation to provide an early power-fail warning, so soft-ware can conduct an orderly system shutdown. The power-fail comparator has a typical input hysteresis of V PFT-HYS and is powered from OUT, making it indepen-dent of the reset circuit. Connect PFI to GND, if not used.
Regulator Output
F ixed output voltages of 1.2V, 1.8V, 2.5V, 3.0V, and 3.3V are available for all devices. The regulator output delivers up to 100mA of load current.
The MAX16024 is available with both fixed and adjustable output-voltage options. Use an external resistive divider network connected between OUT, SET,and GND (Figure 2) to set the adjustable output voltage from 1.8V to 5.25V. Connect SET to GND for parts with fixed output voltage option.
Battery-Backup Circuits with Regulated Output Voltage 12______________________________________________________________________________________
Figure 2. Setting the Adjustable Output Voltage (MAX16024Only)
Applications Information
The MAX16023/MAX16024 are protected for typical short-circuit conditions of 10s or less. Shorting OUT to ground for longer than 10s might damage the device.Bypass V CC and BATT to GND with a 0.1μF capacitor each. Connect a 10μF low-ESR capacitor from OUT to GND. All capacitors should be mounted as close as possible to the device.
Monitoring an Additional Supply
The MAX16023 power-fail comparator can monitor either positive or negative supplies using a resistive divider to PF I (F igures 3 and 4). PFO can be used to generate an interrupt to the μP or to trigger a reset. To monitor a negative supply, connect the top of the resis-tive divider to V CC . Connect the bottom of the resistive divider to the negative voltage to be monitored.
Adding Hysteresis to PFI
The power-fail comparators have a typical input hys-teresis of V PFT-HYS . This is sufficient for most applica-tions where a power-supply line is being monitored through an external voltage-divider (see the Monitoring an Additional Supply section). F igure 5 shows how to add hysteresis to the power-fail comparator. Select the ratio of R1 and R2 such that PF I sees V PFT when V IN falls to the desired trip point (V TRIP ). Resistor R3 adds hysteresis. R3 is typically an order of magnitude greater than R1 or R2. The current through R1 and R2 should be at least 100μA to ensure that the 1μA (max) PF I input current does not shift the trip point. R3 should be larger than 50k Ωto prevent it from loading down PFO .Capacitor C1 adds additional noise rejection.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
______________________________________________________________________________________13
Figure 3. Monitoring an Additional Supply by Connecting PFO to MR
Figure 4. Monitoring a Negative Supply
M A X 16023/M A X 16024
Operation Without a Backup
Power Source
The MAX16023/MAX16024 provide battery-backup functions. If a backup power source is not used, con-nect BATT to GND.
Replacing the Backup Battery
When V CC is above V TH , the backup power source can be removed without danger of triggering a reset pulse.The device does not enter battery-backup mode when V CC stays above the reset threshold voltage.
Negative-Going V CC Transients
The MAX16023/MAX16024 are relatively immune to short duration, negative-going V CC transients.Resetting the μP when V CC experiences only small glitches is usually not desirable. A 0.1μF bypass capacitor mounted close to the V CC pin provides addi-tional transient immunity.
Capacitor Selection and
Regulator Stability
For stable operation, connect a low-ESR 10μF (min) out-put capacitor from OUT to GND. To reduce noise and improve load-transient response and power-supply rejec-tion, use larger output capacitor values.
Battery-Backup Circuits with Regulated Output Voltage
Figure 5. Adding Hysteresis to the Power-Fail Comparator
Part Number Table
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
______________________________________________________________________________________
15
Part Number Table (continued)
Contact factory for availability of nonstandard versions.
M A X 16023/M A X 16024
Battery-Backup Circuits with Regulated Output Voltage 16______________________________________________________________________________________
Typical Applications Circuit
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________17?2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
Package Information
For the latest package outline information and land patterns, go to https://www.doczj.com/doc/9814812567.html,/packages .
Chip Information
PROCESS: BiCMOS